It is a common problem to limit corrosion of surfaces especially metal surfaces which are susceptible to continuing oxidation and especially irons and steels.
It is conventional to firstly remove badly oxidized portions of a metal surface by mechanical abrasion and to remove any remaining oxidized portions by using a strong and quickly acting acid where it is found that the action of the acid can be somewhat more severe upon the oxidized portions than the other unaffected portion of the metal surface and thereby by limiting the period during which the surface is exposed to the acid, a selective removal of oxidized portions can be effected.
It is then well known to treat the thus cleaned metal surface with substances to effect a deposit on the surface which will inhibit subsequent corrosion and among others, phosphoric acid together with accelerators and other substances have been used.
Such a process, while considered reasonably effective particularly with development in the art of phosphating which requires separate steps to first effect the removal of visible rust by mechanical abrasion, apply a first chemical pickling agent which within a set time must be removed or neutralized and finally there must be applied an effective sealant coat.
There has been proposed and are indeed on sale commercial preparations which offer inhibitions of subsequent rusting and these appear to comprise materials which will coat the collective surface that is the oxidized portions as well as the metal in such a way as to limit access thereafter of water and thereby provide an inhibiting effect to subsequent rust promotion.
In tests conducted however we have found that such materials as are presently commercially available, surprisingly have not offered effective long term inhibition of subsequent rusting in the case of mild steel and in the instances tested have actually promoted the rate of corrosion above that of bare metal used in identical conditions as a control.